CN106371098B - One kind having free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination - Google Patents
One kind having free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination Download PDFInfo
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Abstract
The invention discloses one kind free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination, this method specifically: controller exports sine wave by sine-wave generator, excitation ultrasonic transmitter issues ultrasonic wave after the sine wave is amplified by power amplification circuit, while ultrasonic receiver starts to receive ultrasonic wave.Ultrasonic receiver receives ultra-weak electronic signal by carrying out A/D sampling after shaping, amplification, and the FFT transform that the data after sampling are put one by one by DSP data processor obtains the amplitude spectrum and phase spectrum of each point.The difference of the frequency according to corresponding to the range value of certain point in amplitude spectrum and its consecutive points can clearly obtain the frequency variation of the two neighboring point of ultrasonic signal, to accurately determine the frequency inflection point of the ultrasonic ranging system of free decaying vibration.
Description
Technical field
The present invention relates to a kind of measurement methods more particularly to one kind frequency in free decaying vibration ultrasonic ranging system
Inflection point method of discrimination.
Background technique
Sound wave is a kind of mechanical wave, can be divided by vibration frequency: more than 20kHz frequency high frequency region, 20Hz-20kHz frequency
The intermediate frequency zone of rate and low frequency range lower than 20Hz.For frequency in the sound wave of 20kHz or more, vibration frequency exceeded human ear institute
The highest frequency upper limit that can be perceived, thus referred to as ultrasonic wave.Ultrasonic wave has the mechanical waves such as reflection, refraction, diffraction and scattering
The general character.Ultrasonic wave because its vibration frequency compared with high so have some special property: one is power is big, the general sound of energy ratio
Wave is much bigger, there is stronger penetration capacity, can be used as welding, cutting, drilling etc.；The second is wavelength is shorter because of its frequency height,
General barrier size is more much longer than ultrasonic wavelength, therefore its diffracting power is very poor, has good directionality, institute instead
With ultrasonic wave be widely used in industry in non-contact detecting medically.
It is also gradually more stringent to the precise requirements of measurement as the application of ultrasonic distance measurement is gradually popularized.Ultrasonic wave
Spread speed substantially constant in same medium, therefore passed through used in a distance in the medium using measurement ultrasonic wave
Contactless ranging may be implemented in time.Ultrasonic wave is different in the speed of different Propagations, can using this characteristic
To measure the characteristic of medium, the concentration of alcohol is such as measured, measures the temperature etc. of air in boiler.If determining different medium
Ultrasonic Wave Propagation Character, then the type of different material can be measured, such as the quality of sucrose solution, alcoholic solution, various drinks
Characteristic etc..With the development of the society, many occasions are also higher and higher for the required precision of ultrasound detection.In order to improve ranging
Accuracy, it is necessary to elapsed time (pacing the more time) when precise measurement ultrasonic wave is propagated in the medium.
Ultrasonic wave is propagated in non-homogeneous medium will appear the phenomenon that sound wave is gradually decayed with distance, in the mistake of propagation
It can also be influenced by physical conditions such as environment temperatures in journey.In traditional ultrasonic distance measurement, using the ultrasonic wave of 40kHz,
Decay in medium communication process very fast, measurement error is larger when long range measurements, so the ultrasonic distance measurement range of 40kHz compared with
It is small.If selecting ultrasonic frequency too low, cause its directionality bad, when selecting the ultrasonic wave of 25kHz frequency, this frequency
Ultrasonic wave not only can guarantee good directivity, but also can reduce the influence of acoustic attenuation.The ultrasonic wave of suitable frequency is chosen, while utilizing temperature
Scale bar method accurately obtains the speed that ultrasonic wave at identical temperature is propagated, will can gradually decay in ultrasonic wave communication process with
And it is influenced by ambient temperature caused by error be preferably minimized, it might even be possible to ignore.
Ultrasonic receiver is a kind of mechanical vibrator, receives piezoelectric vibrator under electric signal driving, while by bullet
Property power resistance effect, pick-up dipole makees have the forced vibration of damping.Pressure can be generated in the layer close to oscillator surface at this time
Power, this pressure pass to another particle from a particle, i.e. sound wave goes from oscillator surface spread out and forms sound field.It is assumed that receiving
Piezoelectric vibrator nought state (vibration displacement s (t) |T=0=0, vibration velocity s ' (t) |T=0=0) by electric signal underExcitation, telecommunications
NumberThe adaptability to changes of generation isC in formulaaFor the capacitance for receiving piezoelectric vibrator, d33For piezoelectric modulus.Its dynamics
Equation are as follows:
In formula: the quality for receiving piezoelectric vibrator is m, is damped as rs, stiffness Ks(it is decided by transmission piezoelectric oscillator system
Coefficient of elasticity and geometric dimension), s is the displacement for receiving piezoelectric vibrator radiating surface.
When input electrical signal isBringing formula (1) into can obtain:
Due to the effect simultaneously by the resistance of elastic force, pick-up dipole makees the forced vibration for having damping, resonance angular frequency
Rate are as follows:Receive the damped coefficient of piezoelectric vibrator systemWherein RsFor damped coefficient,
msFor mass of system, vibrational state are as follows:
Start to vibrate in nought state due to receiving piezoelectric vibrator, i.e. vibration displacement s (t) |T=0=0, vibration velocity s ' (t)
|T=0=0, i.e.,
Formula (3) abbreviation can obtain:
It is that sinusoidal electric signals are continued for acting on the vibrational state of energy converter above, can be undergone by receiving piezoelectric vibrator by two
Vibrational state: 1. when by tc(Induction Peried) after the time, receiving end oscillator only has the forced vibration of ultrasonic wave to work, that is, shakes
The continuous vibration that the amplitude that dynamic angular frequency is ω is kA reaches displacement amplitude maximum and steady and sustained vibrational state, such as at this time
Fruit electric signal does not stop, and receives piezoelectric vibrator and is constantly in this vibrational state.2. displacement amplitude declines, vibrational state at this time is
With damping vibrition angular frequencyMake the decaying vibration of exponential law for resonance frequency.
As angular frequency=ω of input electrical signals0When, receive the vibration equation of piezoelectric vibrator are as follows:
Above formula is analyzed it is found that reaching stable vibration state from stopping vibration at this time, vibration frequency is resonance angular frequency
Rate ωs0And it remains unchanged, the amplitude of only its vibration of variation.When electric signal stops, receiving piezoelectric vibrator can be with electricity
The vibrational state of signal stop timing is that primary condition makees the free oscillation for having damping.If pumping signal stops after N number of period,
It is answered receiving piezoelectric vibrator vibrational state are as follows:
Piezoelectric vibrator is received in the vibrational state at NT moment: vibration displacement s (t) |T=NTWith vibration velocity s ' (t) |T=NTPoint
Not are as follows:
General solution item will be brought into aboveIt can acquire
By formula (11) it is found that receiving piezoelectric vibrator can be under original vibrational state not after receiving pumping signal and stopping
Until energy is 0, oscillator just stops vibration and so-called " hangover " phenomenon for disconnected decaying.
In conclusion since the spread speed of ultrasonic wave is influenced by ambient temperature, ultrasonic oscillator is acted on by mechanical damping
And can all the precision of range-measurement system be had an impact by generating the factors such as oscillation starting points delay, " hangover ".
Patent " pacing more Method Of Time Measurement based on the ultrasonic wave for having free decaying vibration " is dexterously received using ultrasonic wave
Oscillator has free decaying vibration characteristic, by calculating ultrasonic receiver oscillator forced vibration period and oscillator vibration in there is resistance
The time of Buddhist nun's free oscillating period, available ultrasonic wave pick-up dipole is by ultrasonic exciting frequencies omega and oscillator vibration in there is resistance
Buddhist nun's free running frequency ω 'r.When ultrasonic exciting disappears, ultrasonic wave pick-up dipole can be detached from ultrasonic exciting frequencies omega and
Vibrate in have free decaying vibration frequencies omega 'r.And ultrasonic exciting frequencies omega and have free decaying vibration frequencies omega 'rAll it is
Single-frequency point, controller is by differentiating ω to ω 'rVariation, come identify ultrasonic wave pick-up dipole position ultrasonic exciting believe
Number whether disappear, to be accurately judged to the transition time of ultrasonic wave propagation, effectively improves range accuracy.
But pick-up dipole has the time of free decaying vibration very short, even short several periods, therefore has damping certainly
By vibration frequency ω 'rIt is not easy to reliably detect.
Summary of the invention
In view of the deficiencies of the prior art, it is an object of the present invention to provide one kind free decaying vibration ultrasonic ranging system
Frequency inflection point method of discrimination.
The purpose of the present invention is achieved through the following technical solutions: one kind having free decaying vibration ultrasonic distance measurement system
System frequency inflection point method of discrimination, method includes the following steps:
(1) sine-wave generator exports that n waveform is complete and continuous sine wave signal, the sine wave signal pass through power
Excitation ultrasonic transmitter issues ultrasonic wave after amplifying circuit amplification, while ultrasonic receiver starts to receive ultrasonic wave, ultrasound
The ultra-weak electronic signal of wave receiver output is after signal conditioning circuit amplifies, output to A/D converter.Ultrasonic receiver output
Ultra-weak electronic signal contain ultrasonic receiver oscillator forced vibration state and have and damp own vibrational state two states
Signal, the received ultrasonic frequency of ultrasonic receiver are denoted as ω, and receiver oscillator has free decaying vibration frequency to be denoted as
ω'r。
(2) after the completion of n sinewave output, the id signal S of sine-wave generator output becomes high level from low level,
A/D converter starts to carry out A/D sampling, sample frequency fS, the data of sampling are stored in order in data buffer zone, data
The length of buffer area is X；Meanwhile sine-wave generator exports m waveform completely but the sine wave of phase paraphase.The output of this waveform
After the completion, sine-wave generator no longer output signal.M is natural number, related to the machinery inertial of ultrasonic transmitter, m >=1.
(3) DSP data processor reads the data that A/D is sampled from data buffer zone and carries out FFT transform.It is opened from A/D sampling
The point of beginning successively takes L point D0、D1、D2···DL-1, 1≤L≤2x, 2xIt counts for the data of FFT transform, remaining 2x- L
After point mends 0, FFT transform is carried out.Result after FFT transform is exactly 2xThe plural number of point, each point just correspond to a Frequency point.
The modulus value of this point, is exactly the amplitude characteristic under the frequency values.Frequency interval between adjacent two o'clock is1st point is straight
Flow component, its modulus value are the 2 of DC componentxTimes.The 2nd corresponding frequency of point beIts modulus value is signal in the frequency
The 2 of amplitudex-1Times；The 3rd corresponding frequency of point beIts modulus value is 2 of signal amplitude in the frequencyx-1Times；4th
Putting corresponding frequency isIts modulus value is 2 of signal amplitude in the frequencyx-1Times ... the 2ndxThe corresponding frequency of a point isIts modulus value is 2 of signal amplitude in the frequencyx-1Times.Therefore suitable sample frequency f is selectedSWith it is suitable
Data length L, by FFT transform, available 2xThe signal amplitude value of a frequency point；Select suitable sample frequency fSWith it is suitable
FFT transform data points 2x, the received ultrasonic frequency ω of ultrasonic receiver and receiver oscillator can be had into damping
Vibration frequency ω 'rIt accurately corresponds toIntegral multiple, to obtain ω and ω 'rThe range value A of two frequency bins signalω0、
Aω'r0。
(4) DSP data processor successively takes L point D at the 2nd point from data buffer zone1、D2、D3···DL, remaining 2x-L
After a point mends 0, FFT transform is carried out, ω and ω ' are obtainedrThe range value A of two frequency bins signalω1、Aω'r1, by Aω1、Aω'r1With
Aω0、Aω'r0Successively compare, judges the variation of the two frequency point signal amplitudes.
(5) analogize according to step (4), DSP data processor since i-th point of data buffer zone (i >=3) to X-L point successively
As starting point, L point D are readi-1、Di、Di+1···Di+L-2(3≤i≤X-L), remaining 2xAfter-L points mend 0, carry out
FFT transform obtains ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1, by Aωi-1、Aω'ri-1And Aωi-2、Aω'ri-2
Successively compare, judges the variation of the two frequency point signal amplitudes.
(6) controller is by being respectively compared ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1And Aωi-2、
Aω'ri-2, it is found that AωiIt is gradually reduced, Aω'riIt is gradually increased.Controller is by differentiating certain point, i.e. AωiThe point and A become zeroω'ri
There is the point being not zero, shows that ω frequency signal terminates, ω 'rFrequency signal occurs, which is ultrasonic receiver output electricity
The frequency inflection point of signal.
The invention has the advantages that the present invention takes full advantage of the characteristic of ultrasonic ranging system frequency inflection point, pass through
A/D sampling, DSP data processing method, can accurately and efficiently solve the frequency of the ultrasonic ranging system of free decaying vibration
The test problems of rate inflection point effectively overcome " hangover " phenomenon for having free decaying vibration of ultrasonic wave pick-up dipole, accurate,
Reliably measure ultrasonic wave paces the more time, improves the precision of ultrasonic distance measurement.Experiment shows that measurement error is less than 0.1mm, far
It is much better than the attainable technical level of similar technique institute.The method is of less demanding to hardware circuit, at low cost, data structure is simple
Single, processing speed is fast, is widely used, and is easy to popularization and promotion.
Detailed description of the invention
Fig. 1 is the flow diagram of method of the invention.
Fig. 2 is ultrasonic wave transmitted wave and receives signal in the corresponding relationship of time shaft.
Specific embodiment
Below according to attached drawing the present invention is described in detail, the objects and effects of the present invention will be more apparent.
The present invention, which provides one kind, free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination, as shown in Figure 1,
The ultrasonic ranging system includes that controller, sine-wave generator, power amplification circuit, ultrasonic transmitter, ultrasonic wave connect
Receive device, conditioning circuit, A/D converter, DSP data processor.
The signal of sine-wave generator output motivates ultrasonic transmitter output ultrasonic wave after power amplifier amplifies.Just
String wave producer exports that n waveform be complete and continuous sine wave (in Fig. 2, n=15), and the number n of output waveform is controllable
System, while its output signal, also export an id signal S, when its output signal, S=0, when it does not export letter
Number when, S=1.It is assumed that the time of output waveform is T1, the time of output waveform is not T2.To reduce sine-wave generator output letter
Number stop after, influence of the remained shock of transmitter to receiver, sine-wave generator export n waveform after, add output m wave
The signal period of the complete paraphase of shape guarantees that transmitter does not generate trailing phenomenon (in Fig. 2, m=1).
Ultrasonic receiver receives the ultrasonic wave of ultrasonic transmitter output, and exports as electronic signals.Ultrasonic wave
The ultra-weak electronic signal of receiver output contains ultrasonic receiver oscillator forced vibration state and has the own vibrational state of damping
The signal of two states, the received ultrasonic frequency of ultrasonic receiver are denoted as ω, and receiver oscillator has free decaying vibration
Frequency is denoted as ω 'r。
The ultra-weak electronic signal of receiver output carries out A/D sampling after signal conditioning circuit amplifies, into A/D converter.
A/D converter is using TMS320F28335 type digital signal processor as core, TMS320F28335 type digital signal processor tool
There is the high speed processing ability of 150MHz, have 32 floating point processing units, 6 DMA channels support ADC and 12 16 channel ADC.
Sample rate is fs, (f in Fig. 2s=128kHz), as a result sampling number X is stored in data buffer area.
DSP data processor reads the data of A/D sampling from data buffer zone.Assuming that receiving signal after A/D sampling
Peak value be H, then the modulus value of each point of the result of FFT is exactly the 2 of Hx-1Times.So, first point is exactly DC component,
Its modulus value is exactly the 2 of DC componentxTimes.And the phase of each point is exactly the phase of the signal under the frequency.First point
It indicates DC component (i.e. 0Hz), and the last one point 2xNext one point then indicate sample frequency fs, this intermediate waveform quilt
2x- 1 point is divided into 2xThe frequency of equal portions, each point is incremented by successively.Assuming that frequency represented by certain point n are as follows: fn=(n-1)
fs/2x.The f it can be seen from above formulanCan differentiate to frequency is fs/2xIf sample frequency is 1024Hz, sampled point
Number is 1024 points, then can differentiate 1Hz.1024 points of the sample rate of 1024Hz is just 1 second, in other words, adopts
The signal of 1 second time of sample is simultaneously FFT, then result can analyze 1Hz, if sampling the signal of 2 second time and being FFT, ties
Fruit can analyze 0.5Hz.Frequency resolution and sampling time are reciprocal relations, if increasing sampling number, i.e. sampling time,
Frequency resolution can be improved.Assuming that certain point n is indicated with plural number a+bi after FFT, wherein the real part and void of plural a+bi
Portion respectively indicates signal in n point amplitude and phase.So this plural mould is exactlyPhase is exactlyAssuming that our points since being sampled A/D successively take L point D0、D1、D2···DL-1, 1≤L≤2x, 2x
It counts for the data of FFT transform, remaining 2xAfter-L points mend 0, FFT transform is carried out.Result after FFT transform is exactly 2xPoint
Plural number, each point just correspond to a Frequency point.The modulus value of this point, is exactly the amplitude characteristic under the frequency values.Adjacent two
Point between frequency interval be1st point is DC component, its modulus value is the 2 of DC componentxTimes.2nd point is corresponding
Frequency isIts modulus value is 2 of signal amplitude in the frequencyx-1Times；The 3rd corresponding frequency of point beIts modulus value
It is 2 of signal amplitude in the frequencyx-1Times；The 4th corresponding frequency of point beIts modulus value is signal width in the frequency
The 2 of valuex-1Times ... the 2ndxThe corresponding frequency of a point isIts modulus value is 2 of signal amplitude in the frequencyx-1
Times.Therefore suitable sample frequency f is selectedSWith suitable data length L, by FFT transform, available 2xThe letter of a frequency point
Number range value；Select suitable sample frequency fSWith suitable FFT transform data points 2x, can be by ω and ω 'rIt is accurate corresponding
InIntegral multiple, to obtain ω and ω 'rThe range value A of two frequency bins signalω0、Aω'r0.DSP data processor is from data
The 3rd point of buffer area starts successively to be used as starting point to X-L point, successively takes L point Di、Di+1、Di+2···Di+L-1(3≤i≤X-
L) remaining 2xAfter-L points mend 0, FFT transform is carried out, ω and ω ' are obtainedrThe range value A of two frequency bins signalωi、Aω'ri, will
Aωi、Aω'riAnd Aωi-1、Aω'ri-1Successively compare, judges the variation of the two frequency point signal amplitudes.Controller is read by successively
Compare ω and ω 'rThe range value A of two frequency bins signalωi、Aω'riAnd Aωi-1、Aω'ri-1, it is found that AωiIt is gradually reduced, Aω'riBy
It is cumulative big.Controller is by differentiating certain point, i.e. AωiThe point and A become zeroω'riThere is the point being not zero, which is frequency
Inflection point.
According to the above results, so that it may accurately determine the frequency of the ultrasonic ranging system of free decaying vibration
Inflection point.Ultrasonic wave can be accurately obtained using the frequency inflection point method of discrimination for the ultrasonic ranging system for having free decaying vibration
The transition time of transmission, to improve the precision of ultrasonic ranging system.
In Fig. 1, sine-wave generator is driven by controller, the signal of sine-wave generator output is through power amplifier
Ultrasonic transmitter output ultrasonic wave is motivated after amplification.After ultrasonic transmitter is by transmission, ultrasonic signal is transmitted to reception
Device.The ultra-weak electronic signal of receiver output carries out A/D sampling, the number obtained after A/D is sampled after signal conditioning circuit amplifies
FFT data analysis is carried out according to by DSP data processor, the result of analysis transfers back to the memory in controller.
In Fig. 2, signal, id signal, ultrasonic signal, the ultrasonic wave for respectively describing sine-wave generator output are received
Signal corresponding relationship on a timeline after device output signal, A/D sampled signal and FFT transform.By (5) in Fig. 2 as it can be seen that A/
D sampling can convert digital signal for the analog signal in ultrasonic wave.By (6) in Fig. 2 as it can be seen that the point after A/D sampling
After grouping, after group carries out FFT transform one by one, the amplitude spectrum and phase spectrum of the available each point of ultrasonic signal, according to amplitude
Certain point frequency difference corresponding with the range value of its consecutive points in spectrum can clearly obtain the two neighboring point of ultrasonic signal
Frequency variation, to determine the inflection point of frequency.
Embodiment: the present embodiment has free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination, specifically includes
Following steps:
(1) sine-wave generator exports that n waveform is complete and continuous sine wave signal, the sine wave signal pass through power
Excitation ultrasonic transmitter issues ultrasonic wave after amplifying circuit amplification, while ultrasonic receiver starts to receive ultrasonic wave, ultrasound
The ultra-weak electronic signal of wave receiver output is after signal conditioning circuit amplifies, output to A/D converter.
(2) after the completion of n sinewave output, the id signal S of sine-wave generator output becomes high level from low level,
A/D converter starts to carry out A/D sampling, sample frequency fS(fs=128kHz), the data of sampling are stored in order slow in data
It rushes in area, the length of data buffer zone is X；Meanwhile sine-wave generator exports m waveform completely but the sine of phase paraphase
Wave.After the completion of the output of this waveform, sine-wave generator no longer output signal.M is natural number, used with the machinery of ultrasonic transmitter
Property related, m >=1.
(3) DSP data processor reads the data that A/D is sampled from data buffer zone and carries out FFT transform.It is opened from A/D sampling
The point of beginning successively takes 40 point D0、D1、D2···D39, 2xIt counts for the data of FFT transform, remaining 2xAfter -40 points mend 0,
Carry out FFT transform.Result after FFT transform is exactly 2xThe plural number of point, each point just correspond to a Frequency point.This point
Modulus value is exactly the amplitude characteristic under the frequency values.Frequency interval between adjacent two o'clock is1st point is DC component,
Its modulus value is the 2 of DC componentxTimes.The 2nd corresponding frequency of point beIts modulus value is signal amplitude in the frequency
2x-1Times；The 3rd corresponding frequency of point beIts modulus value is 2 of signal amplitude in the frequencyx-1Times；4th point is corresponding
Frequency beIts modulus value is 2 of signal amplitude in the frequencyx-1Times ... the 2ndxThe corresponding frequency of a point isIts modulus value is 2 of signal amplitude in the frequencyx-1Times.Therefore suitable sample frequency f is selectedSWith it is suitable
Data length L, by FFT transform, available 2xThe signal amplitude value of a frequency point；Select suitable sample frequency fSWith it is suitable
FFT transform data points 2x, can be by ω and ω 'rIt accurately corresponds toIntegral multiple, to obtain ω and ω 'rTwo frequencies
The range value A of point signalω0、Aω'r0。
(4) DSP data processor successively takes 40 point D at the 2nd point from data buffer zone1、D2、D3···D40, remaining
2xAfter -40 points mend 0, FFT transform is carried out, ω and ω ' are obtainedrThe range value A of two frequency bins signalω1、Aω'r1, by Aω1、Aω'r1
And Aω0、Aω'r0Successively compare, judges the variation of the two frequency point signal amplitudes.
(5) analogize according to step (4), DSP data processor since the 3rd point of data buffer zone to X-39 point successively as
Initial point reads 40 point Di-1、Di、Di+1、Di+2···Di+38(3≤i≤X-39) remaining 2xAfter -40 points mend 0, carry out
FFT transform obtains ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1, by Aωi-1、Aω'ri-1And Aωi-2、Aω'ri-2
Successively compare, judges the variation of the two frequency point signal amplitudes.
(6) controller is by being respectively compared ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1And Aωi-2、
Aω'ri-2, it is found that AωiIt is gradually reduced, Aω'riIt is gradually increased.Controller is by differentiating certain point, i.e. AωiThe point and A become zeroω'ri
There is the point being not zero, shows that ω frequency signal terminates, ω 'rFrequency signal occurs, which is ultrasonic receiver output electricity
The frequency inflection point of signal.
One of core technology main points of the invention patent are to use FFT Fast Fourier Transform (FFT), according in amplitude spectrum
Whether the corresponding point relative position in different cycles of a certain fixed frequency shifts, and can clearly obtain ultrasonic signal
The frequency in two neighboring period changes, to determine the inflection point of frequency.
The two of the core technology main points of the invention patent are that DSP data processor can using DSP data processor
The digital signal exported to ultrasonic receiver after each A/D sampling carries out FFT transform, and processing speed is fast, high-efficient.
The core technology third key point of the invention patent be use TMS320F28335 type digital signal processor into
Row A/D conversion, TMS320F28335 type digital signal processor is floating-point type controller, with previous fixed point type controller phase
Than the precision of the device is high, and at low cost, small power consumption, performance is high, and peripheral hardware integrated level is high, and data storage capacity is big, and A/D conversion is more smart
Really quickly.
The present invention takes full advantage of the characteristic of the ultrasonic ranging system frequency inflection point of free decaying vibration, Ke Yizhun
Really, effectively measuring ultrasonic wave paces the more time, improves the precision of ultrasonic distance measurement.Experiment, which shows to measure using the method, to be missed
Difference is less than 0.1m and is far superior to the attainable technical level of similar technique institute.
Claims (2)
1. one kind has free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination, which is characterized in that this method includes
Following steps:
(1) sine-wave generator exports that n waveform is complete and continuous sine wave signal, the sine wave signal pass through power amplification
Excitation ultrasonic transmitter issues ultrasonic wave after circuit amplification, and while ultrasonic transmitter issues ultrasonic wave, ultrasonic wave is received
Device starts to receive ultrasonic wave, and after signal conditioning circuit amplifies, output to A/D turns the ultra-weak electronic signal of ultrasonic receiver output
Parallel operation；The ultra-weak electronic signal of ultrasonic receiver output includes ultrasonic receiver oscillator forced vibration state and has damping own
The signal of vibrational state two states, the received ultrasonic frequency of ultrasonic receiver are denoted as ω, and receiver oscillator has damping
Free running frequency is denoted as ω 'r；
(2) after the completion of n sinewave output, the id signal S of sine-wave generator output becomes high level, A/D from low level
Converter starts to carry out A/D sampling, sample frequency fS, the data of sampling are stored in order in data buffer zone, and data are slow
The length for rushing area is X；While A/D converter starts to carry out A/D sampling, sine-wave generator exports m waveform completely but phase
The sine wave of position paraphase；After the completion of the output of this waveform, sine-wave generator no longer output signal；M is natural number, is sent out with ultrasonic wave
The machinery inertial of emitter is related, m >=1；
(3) DSP data processor reads the data that A/D is sampled from data buffer zone and carries out FFT transform；Since A/D sampling
Point successively takes L point D0、D1、D2···DL-1, 1≤L≤2x, 2xIt counts for the data of FFT transform, remaining 2x- L points mend 0
Afterwards, FFT transform is carried out；Result after FFT transform is exactly 2xThe plural number of point, each puts a corresponding Frequency point；This point
Modulus value is exactly the amplitude characteristic under the frequency values；Frequency interval between adjacent two o'clock isThe 1st corresponding frequency of point be
0Hz, its modulus value are the 2 of DC componentxTimes；N-th point of corresponding frequency beIts modulus value is in the frequency
The 2 of signal amplitudex-1Times, 1 n≤2 <x；Therefore suitable sample frequency f is selectedSWith suitable data length L, become by FFT
It changes, available 2xThe signal amplitude value of a frequency point；Select suitable sample frequency fSWith suitable FFT transform data points 2x,
Can by the damping vibrition frequencies omega of the received ultrasonic frequency ω of ultrasonic receiver and receiver oscillator 'rIt is accurate corresponding
InIntegral multiple, to obtain ω and ω 'rThe range value A of two frequency bins signalω0、Aω'r0；
(4) DSP data processor successively takes L point D at the 2nd point from data buffer zone1、D2、D3···DL, remaining 2x- L points
After mending 0, FFT transform is carried out, ω and ω ' are obtainedrThe range value A of two frequency bins signalω1、Aω'r1, by Aω1、Aω'r1And Aω0、
Aω'r0Successively compare, judges the variation of the two frequency point signal amplitudes；
(5) analogize according to step (4), DSP data processor is since i-th point of data buffer zone (i >=3) to the successively conduct of X-L point
Starting point reads L point Di-1、Di、Di+1···Di+L-2(3≤i≤X-L), remaining 2xAfter-L points mend 0, FFT change is carried out
It changes, obtains ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1, by Aωi-1、Aω'ri-1And Aωi-2、Aω'ri-2Successively compare
Compared with judging the variation of the two frequency point signal amplitudes；
(6) controller is by being respectively compared ω and ω 'rThe range value A of two frequency bins signalωi-1、Aω'ri-1And Aωi-2、Aω'ri-2,
It can find AωiIt is gradually reduced, Aω'riIt is gradually increased；Controller is by differentiating certain point, i.e. AωiThe point and A become zeroω'riOccur not
The point for being zero shows that ω frequency signal terminates, ω 'rFrequency signal occurs, which is ultrasonic receiver output electric signal
Frequency inflection point.
2. one kind according to claim 1 has free decaying vibration ultrasonic ranging system frequency inflection point method of discrimination,
It is characterized in that, in the step 2, the sampling of A/D converter specifically: empty transformation result number first after A/D converter starting
According to buffer area, in case the sampled data of last time is on currently causing the unnecessary error to influence；A/D converter conversion resolution is set
8 are set to, sample frequency fs=128kHz, is as a result stored in data buffer area.
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